CN111929276A - Double-expiratory molecule measuring method and system based on cavity ring-down spectroscopy - Google Patents
Double-expiratory molecule measuring method and system based on cavity ring-down spectroscopy Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000000180 cavity ring-down spectroscopy Methods 0.000 title claims abstract description 15
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims abstract description 150
- RRHGJUQNOFWUDK-UHFFFAOYSA-N Isoprene Chemical compound CC(=C)C=C RRHGJUQNOFWUDK-UHFFFAOYSA-N 0.000 claims abstract description 117
- 230000000241 respiratory effect Effects 0.000 claims abstract description 59
- 238000010521 absorption reaction Methods 0.000 claims abstract description 57
- 239000007789 gas Substances 0.000 claims abstract description 55
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 claims abstract description 48
- 238000005259 measurement Methods 0.000 claims abstract description 28
- 239000001272 nitrous oxide Substances 0.000 claims abstract description 20
- 238000004458 analytical method Methods 0.000 claims abstract description 13
- 230000029058 respiratory gaseous exchange Effects 0.000 claims abstract description 11
- UBAZGMLMVVQSCD-UHFFFAOYSA-N carbon dioxide;molecular oxygen Chemical compound O=O.O=C=O UBAZGMLMVVQSCD-UHFFFAOYSA-N 0.000 claims abstract description 5
- 230000002452 interceptive effect Effects 0.000 claims abstract description 4
- 238000012216 screening Methods 0.000 claims abstract description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 25
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 22
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 12
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 12
- 239000001569 carbon dioxide Substances 0.000 claims description 12
- 229910052760 oxygen Inorganic materials 0.000 claims description 12
- 239000001301 oxygen Substances 0.000 claims description 12
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 11
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 11
- -1 0-2 ppmv) Chemical compound 0.000 claims description 10
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 10
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 8
- 238000007405 data analysis Methods 0.000 claims description 8
- 229910001868 water Inorganic materials 0.000 claims description 8
- 238000011410 subtraction method Methods 0.000 claims description 7
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims description 6
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical compound CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 6
- 210000004072 lung Anatomy 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 6
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 5
- 235000019441 ethanol Nutrition 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 238000011010 flushing procedure Methods 0.000 claims description 4
- 238000012545 processing Methods 0.000 claims description 4
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 3
- 229910021529 ammonia Inorganic materials 0.000 claims description 3
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 3
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 2
- 238000004364 calculation method Methods 0.000 claims description 2
- 230000008030 elimination Effects 0.000 claims description 2
- 238000003379 elimination reaction Methods 0.000 claims description 2
- 239000003550 marker Substances 0.000 claims description 2
- 229910000069 nitrogen hydride Inorganic materials 0.000 claims description 2
- 238000001228 spectrum Methods 0.000 claims 1
- 206010058467 Lung neoplasm malignant Diseases 0.000 abstract description 2
- 201000005202 lung cancer Diseases 0.000 abstract description 2
- 208000020816 lung neoplasm Diseases 0.000 abstract description 2
- 230000004060 metabolic process Effects 0.000 abstract description 2
- 230000003287 optical effect Effects 0.000 abstract 1
- 229960001730 nitrous oxide Drugs 0.000 description 16
- 239000000126 substance Substances 0.000 description 9
- 238000001514 detection method Methods 0.000 description 5
- 235000012055 fruits and vegetables Nutrition 0.000 description 4
- 201000010099 disease Diseases 0.000 description 3
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 235000013842 nitrous oxide Nutrition 0.000 description 3
- 206010033546 Pallor Diseases 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000012855 volatile organic compound Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000090 biomarker Substances 0.000 description 1
- 238000001307 laser spectroscopy Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/39—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using tunable lasers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N33/497—Physical analysis of biological material of gaseous biological material, e.g. breath
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Abstract
The invention discloses a double-expiration molecule measuring method based on optical cavity ring-down spectroscopy, which comprises the steps of firstly, carrying out respiration interference analysis on main components in respiratory gas in an ultraviolet region, and screening out laser wavelength 257nm which can be used for measuring respiratory isoprene; the following discusses the practical implementation and feasibility of using background subtraction to subtract the absorption of two interfering small atmospheric molecules (oxygen, carbon dioxide) and the known concentration of exhaled molecular acetone, and neglecting the weak absorption of nitrous oxide, and provides a new non-invasive, fast and reliable means for near real-time, on-line measurement of acetone and isoprene, two exhaled molecules involved in lung cancer metabolism.
Description
Technical Field
The invention relates to the technical field of biomedicine, in particular to a measuring method capable of simultaneously measuring the contents of acetone and isoprene in exhaled air of a human body based on a cavity ring-down spectroscopy technology.
Background
The main challenge of applying CRDS to near real-time online analysis of exhaled breath is to firstly, the analysis means based on laser technology is mainly used to study single identifiable molecules or respiratory markers that have been determined to be associated with a certain disease, and often only one exhaled molecule can be detected at a single time, but one of the main difficulties faced by researchers in the preliminary exploration phase of the respiratory research field at present is that most respiratory VOCs are not associated with a specific disease one-to-one, so that an instrument that can only detect a single exhaled molecule is not sufficient. At this point, it is important to have an instrument that can analyze multiple respiratory VOCs, and the measurement of multiple respiratory molecules can provide a large enough sample size to look for more specific correlations between respiratory biomarkers and physiological indicators of disease.
Secondly, the sensitivity of the laser spectroscopy depends on the wavelength of the laser used, which is the critical parameter of CRDS, and firstly determines the absorption cross section of the substance to be detected, and thus the detection limit of the substance to be detected. And secondly, the spectral interference brought by the absorption of other gas molecules in the human body breathing gas at the position to the measurement of the substance to be measured is determined, and because the position of the absorption wavelength only having the substance to be measured is difficult to find, the influence of atmospheric molecules is usually deducted by adopting a background deduction method in an actual situation, or the influence of non-substance to be measured is deducted by adopting a dual-wavelength background deduction method.
Therefore, a method for simultaneously measuring the content of acetone and isoprene in the exhaled air of a human body based on CRDS is provided.
Disclosure of Invention
The invention mainly aims at a method for measuring two expiratory molecules of acetone and isoprene in human respiratory gas based on Cavity Ringdown Spectroscopy (CRDS). The invention provides a method and a system for measuring breath molecules with double wavelengths on the basis of which the feasibility of measuring breath acetone at 266nm by using a background subtraction method can be verified, which can meet the requirement that the influence of non-to-be-measured substances can be subtracted by using the double-wavelength background subtraction method, and can provide a novel noninvasive, rapid and reliable means for near-real-time and online measurement of two breath molecules, namely acetone and isoprene, which are related to lung cancer metabolism, so as to solve the problems provided by the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: the method for realizing the invention comprises the following steps:
a double-expiration molecule measuring method based on cavity ring-down spectroscopy comprises the steps of measuring the main components, the content and the absorption cross section of human respiratory gas, and is characterized by comprising the following steps:
s1, carrying out respiratory interference analysis on main components in respiratory gas;
s2, screening M (M is more than or equal to 2, and M is a natural number) target elements serving as breathing markers, and selecting laser wavelength for measuring the target elements;
and S3, removing respiratory interference elements.
Further, S11, at an absorption cross section of 257nm, the respiratory gas content of the human body is respectively measured, wherein the respiratory gas content comprises four atmospheric molecules of nitrogen, water, oxygen and carbon dioxide, and the contents are respectively as follows: nitrogen (N2, 78.04%), water (H2O, 6%), oxygen (O2, 16%), carbon dioxide ( CO 2, 5%);
s12, measuring the content of the inorganic component with higher content, wherein the content is as follows: ammonia (NH3, 0-2 ppmv), methane (CH4, 2-10ppmv), carbon monoxide (CO, 1-10 ppmv), nitric oxide (NO, 10-50 ppmv), nitrous oxide (N2O,1-20 ppmv), isoprene (C5H8, 50-200 ppmv), acetone (C3H8O, 0-1 ppmv), ethane (C2H6, 0-10 ppmv), pentane (C5H12, 0-10 ppmv),
methanol (CH3OH, 0-10 ppbv), ethanol (C2H5OH, 0-10 ppbv), propanol (C3H7OH, 0-10 ppbv);
s13, excluding the respiratory gas with the absorption section of 0 at 257nm, and analyzing the interference influence of the rest respiratory gas on the target element serving as the respiratory marker.
Further, s21. screen out 2 target elements as respiratory markers: isoprene and acetone;
and S22, according to the data measured in S11, S12 and S13, carrying out respiratory disturbance analysis on oxygen, carbon dioxide and nitrous oxide which disturb target elements in respiratory gas.
Further, S31, eliminating the influence on oxygen and carbon dioxide in the breathing gas, which interfere with the target element, by a background subtraction method;
s32, performing direct elimination treatment on nitrous oxide interfering with target elements in the breathing gas;
s33, eliminating the influence of acetone on isoprene through a double-expiration molecule measuring system based on cavity ring-down spectroscopy on the interference between target element isoprene and the interior of acetone.
Furthermore, the double-expiration molecular measurement system based on the cavity ring-down spectroscopy comprises a 266nm measurement module and a 257nm measurement module, wherein each measurement module is provided with a respective laser output system, a pressure-controlled vacuum cavity, a high-reflection mirror, a data acquisition and analysis module and a sample injection system; the 266nm measurement module and the 257nm measurement module share one data analysis module, the laser output system is composed of a laser with the emergent wavelength of 266nm or 257nm, the laser emits laser light and enters the vacuum cavity through the first reflector and the second reflector, 99% of the laser light is reflected back and forth between the first high reflector 7 and the second high reflector 8, and a small part of the laser light transmitted from the second high reflector 8 is collected by the photomultiplier after being reflected by the fourth reflector 4 and the third reflector 3 and then enters the data analysis module for data processing.
Further, S33 includes
S331, measuring the concentration of acetone in the gas sample by using a 266nm laser;
s332, calculating the absorption intensity of the acetone at 257nm, and deducting the absorption intensity of the acetone from the overall absorption intensity at 257nm to obtain the effective absorption intensity of the isoprene at 257 nm.
Further, S33 includes
S331, measuring the concentration of acetone in the gas sample by using a 266nm laser;
s332, calculating the absorption intensity of the acetone at 257nm, and deducting the absorption intensity of the acetone from the overall absorption intensity at 257nm to obtain the effective absorption intensity of the isoprene at 257 nm.
Further, S332 includes
First, in the 266nm module, the ring down time τ for background air in the vacuum chamber 22 is measuredAir (a)After the measurement is completed, the background air in the vacuum chamber 22 is pumped away using the molecular pump 27, and high purity nitrogen is usedAir-flushing the vacuum chamber 22 three times;
then, collecting respiratory gas of a subject, and slowly and uniformly blowing the lung gas into the vacuum cavity by the subject through a disposable mouthpiece;
the gas sample is introduced into the vacuum chamber 22 to an atmospheric pressure, and the ring-down time τ at that time is measuredBreath sampleCalculating the particle number density n of the breath acetone according to the formula (1)Breath acetoneWherein d is the length of the cavity 50cm, and c is the speed of light 3 x 108m/s，σBreath acetone(266nm) is the absorption cross section of acetone at 266nm 4.5 x 10-20cm2/mol，
Subsequently, in the 257nm module, the ring down time τ 'of background air in the vacuum cavity 23 is measured'Air (a)After the measurement is finished, the molecular pump 26 is used for pumping the background air in the vacuum cavity 23 away, and high-purity nitrogen is used for flushing the vacuum cavity 23 for three times;
followed by the collection of respiratory gases from the subject. The testee blows the lung gas into the vacuum cavity slowly and uniformly through the disposable mouthpiece,
the gas sample is introduced into the vacuum chamber 23 to one atmosphere, and the ring down time τ 'at this time is measured'Breath sampleCalculating the effective absorption A 'of acetone and isoprene at 257nm according to the formula (2)'Breath sample
According to S31, formula (2) uses a background subtraction method to subtract the effects of oxygen and carbon dioxide, so that the effective absorption a' breath sample at 257nm is due to respiratory acetone, respiratory isoprene and respiratory nitrous oxide together, and the weak absorption of nitrous oxide at 257nm is ignored, that is:
| A′breath sample＝A′Breath acetone+A′Respiratory isoprene | (3) |
In equation (4), n breath acetone has been measured in the first step, and a' breath acetone can be calculated according to equation (4), wherein σ breath acetone (257nm) is 3.412 × 10-20cm 2/mol:
| A′breath acetone＝σBreath acetone(257nm)nBreath acetoned | (4) |
In formula (3), A 'is known'Breath acetoneAnd A'Breath sampleTherefore, A 'can be calculated'Respiratory isoprene，
After a' respiratory isoprene is obtained, n respiratory isoprene can be calculated according to formula (5), wherein the sigma respiratory isoprene (257nm) is 2.5 × 10-20cm 2/mol:
| A′respiratory isoprene＝σRespiratory isoprene(257nm)nRespiratory isoprened | (5) |
Since n isBreath acetoneAnd nRespiratory isopreneRespectively represent the number density of particles of acetone and isoprene in cm-3It can be further converted to volume fractions of acetone and isoprene, calculated as (6):
compared with the prior art, the invention has the beneficial effects that:
the invention can play an all-dimensional cleaning and sterilizing role without dead angles on the fruits and vegetables through the cleaning device, thereby ensuring that the fruits and vegetables are safer and more sanitary after blanching, and in addition, the invention can also ensure that the fruits and vegetables are blanched uniformly when blanching different fruits and vegetables.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic view of a measurement method according to the present invention;
in the figure: 1-a first mirror 1; 2-a second mirror 2; 3-third mirror 3; 4-a fourth mirror 4; 5-photomultiplier B; 6-pressure gauge B; 7-a first high-reflection mirror 7; 8-a second high-reflection mirror 8; 9-data analysis module 9; 10-sample inlet B; 11-gas outlet B; 12-mirror a; 13-mirror B; 14-mirror D; 15-mirror C; 16-photomultiplier tube A; 17-pressure gauge a; 18-high reflection mirror A; 19-high reflection mirror B; 20-sample inlet A; 21-air outlet A; 22-vacuum chamber B; 23-vacuum chamber a; 24-laser a; 25-laser B; 26-molecular pump a; 27-molecular pump B.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-2, the present invention provides a technical solution:
in the ultraviolet region at 257nm, a respiratory interference analysis was performed on the main components in the respiratory gas.
The content of the main component in the human respiratory gas and the absorption cross section at 257nm were tested and are shown in table one:
in table one, n.a. indicates absorption, but the absorption cross section is unclear.
The respiratory gases of the human body include four major atmospheric molecules: nitrogen (N)2, 78.04%), water (C)H2O, 6%) oxygen (O)216%), carbon dioxide (CO)25%) of a relatively high content of inorganic components including ammonia (NH)30-2 ppmv), methane (CH)42-10ppmv), carbon monoxide (CO, 1-10 ppmv), nitrogen monoxide (NO, 10-50 ppmv), dinitrogen monoxide (N)2O,1-20ppbv), isoprene (C)5H850-200 ppbv), acetone (C)3H8O, 0-1 ppmv), ethane (C)2H60-10 ppbv), pentane (C)5H120-10 ppbv), methanol (CH)3OH, 0-10 ppbv), ethanol (C)2H5OH, 0-10 ppbv) and propanol (C)3H7OH, 0-10 ppbv), and the like. At 257nm, the substances present for absorption include, in addition to the molecule isoprene to be detected, oxygen, carbon dioxide, nitrous oxide and acetone, and these four substances are subjected to interference analysis.
The two molecules, oxygen and carbon dioxide, belong to atmospheric molecules and are present in air in a small amount different from the respiratory gas, so that part of the influence can be eliminated by background subtraction.
Dinitrogen monoxide has an absorption cross section at 257nm of about 5 x 10-24cm2Permol, is the isoprene absorption cross section (2.5X 10)-20 cm2/mol) 1/5000; the concentration of nitrous oxide is about 20ppbv, which is 1/10 of the isoprene concentration, so the absorption intensity of nitrous oxide at 257nm is 1/50000 of that of isoprene, which is several orders of magnitude lower than that of isoprene, so the weak absorption of nitrous oxide at 257nm can be ignored.
At 257nm, absorption cross section due to acetone (3.412 x 10)-20 cm2/mol) and concentration are greater than that of isoprene, so the absorption intensity of acetone is also greater than that of isoprene, and therefore the absorption of acetone cannot be neglected when measuring isoprene. In order to solve the problem of interference on isoprene measurement caused by the absorption of respiratory acetone at 257nm, the method firstly uses a 266nm laser to measure the acetone concentration in a gas sample, substitutes the known acetone concentration into a formula to calculate the absorption intensity of acetone at 257nm, and obtains the integral absorption at 257nmThe absorption intensity of acetone is subtracted from the intensity, so that the effective absorption intensity of isoprene with the wavelength of 257nm is obtained, 266nm and 257nm are respectively selected as detection wavelengths of breath acetone and isoprene, and the detection of the breath acetone and isoprene can be realized by combining a background subtraction method.
Referring to fig. 1, the overall structure of the present invention mainly includes a multi-wavelength laser output system, a pressure-controlled vacuum chamber, a high-reflection mirror, a data acquisition and analysis module, a sample injection system, etc.
The 266nm module and the 257nm module are respectively provided with a laser output system, a pressure-controlled vacuum cavity, a high-reflection mirror, a data acquisition module and a sample introduction system, and share one data analysis module 9.
The invention adopts an on-line sample introduction mode, does not need to carry out sample pretreatment, and in a 266nm module and a 257nm module, a gas sample respectively enters a vacuum cavity through a sample inlet 10 and a sample inlet 20, and is pumped away by a molecular pump 26 and a molecular pump 27 through a gas outlet 11 and a gas outlet 21, so that no gas residue exists in the cavity, and after each measurement is finished, the cavity is flushed by high-purity nitrogen.
The pressure in the vacuum cavity is accurately measured through the pressure gauge 6 and the pressure gauge 17, the effect of pressure automatic adjustment and pressure stabilization is realized, and the accuracy and the repeatability of the measuring result are determined.
The basic principle of the 266nm module is: the wavelength laser output system is composed of a laser 25 with the outgoing wavelength of 266nm, after the laser 25 emits laser, the laser enters a vacuum cavity 22 through a first reflective mirror 1 and a second reflective mirror 2, 99% of the laser is reflected back and forth between a first high reflective mirror 7 and a second high reflective mirror 8, a small part of the laser transmitted from the second high reflective mirror 8 is collected by a photomultiplier 5 after being reflected by a fourth reflective mirror 4 and a third reflective mirror 3, and then enters a data analysis module 9 for data processing.
The basic principle of the 257nm module is: the wavelength laser output system is composed of a laser 24 with the emitting wavelength of 257nm, after the laser 24 emits laser, the laser enters a vacuum cavity 23 through a reflective mirror 12 and a reflective mirror 13, 99% of the laser is reflected back and forth between a high reflecting mirror 18 and a high reflecting mirror 19, after a small part of the laser transmitted from the high reflecting mirror 19 is reflected through a reflective mirror 15 and a reflective mirror 14, the laser is collected by a photomultiplier 16 and then enters a data analysis module 9 for data processing.
The working principle is as follows: the method adopts a background gas deduction method to calculate the concentrations of acetone and isoprene in the human body breathing gas. Firstly, the concentration of the respiratory acetone is measured at 266nm by using a background deduction method, and aiming at four substances which have interference on isoprene measurement, namely oxygen, carbon dioxide, nitrous oxide and acetone, the influence of the oxygen and the carbon dioxide is eliminated by using the background deduction method in real time by different processing methods. The absorption intensity of nitrous oxide at 257nm is several orders of magnitude lower than that of isoprene, so the weak absorption of nitrous oxide at 257nm is ignored. The method comprises the steps of substituting the known acetone concentration into a formula to calculate the absorption intensity of acetone at 257nm, deducting the absorption intensity of acetone from the overall absorption intensity at 257nm to further obtain the effective absorption intensity of isoprene at 257nm, selecting 266nm and 257nm as detection wavelengths of breath acetone and isoprene respectively, and combining a background deduction method to realize the detection of breath acetone and isoprene in human breath.
The measuring method comprises the following steps:
first, in the 266nm module, the ring down time for background air in the vacuum chamber 22 was measured
After the measurement is completed, the background air in the vacuum chamber 22 is pumped away using the molecular pump 27, and the vacuum chamber 22 is flushed three times with high purity nitrogen gas. Followed by the collection of respiratory gases from the subject. The testee blows the lung gas into the vacuum cavity slowly and uniformly through the disposable mouthpiece. The gas sample is introduced into the vacuum chamber 22 to an atmospheric pressure, and the ring-down time at this time is measured
Calculating the particle number density of breath acetone according to the formula (1)
. Wherein
The length of the cavity is 50cm,
at the speed of light 3 x 108m/s，
The absorption cross section of acetone at 266nm is 4.5 x 10-20 cm2/mol。
 |
（1） |
Subsequently, in the 257nm module, the ring down time for the background air in the vacuum chamber 23 was measured, the background air in the vacuum chamber 23 was pumped away using the molecular pump 26 after the measurement was completed, and the vacuum chamber 23 was flushed three times with high purity nitrogen gas. Followed by the collection of respiratory gases from the subject. The testee blows the lung gas into the vacuum cavity slowly and uniformly through the disposable mouthpiece. The gas sample was introduced into the vacuum chamber 23 to one atmosphere, the ring-down time at this time was measured, and the effective absorption at 257nm of acetone and isoprene was calculated according to the formula (2).
 | （2） |
From the above analysis, formula (2) uses a background subtraction method to subtract the effects of oxygen and carbon dioxide. Thus, the effective absorption at 257nm is due to respiratory acetone, respiratory isoprene and respiratory nitrous oxide together, as the weak absorption of nitrous oxide at 257nm is neglected, i.e.:
 | （3） |
in equation (4), having been obtained from the first measurement step, it can be calculated from equation (4) that is 3.412 by 10-20cm 2/mol:
 | （4） |
in the formula (3), it is known
And
thus, can calculate
。
After this is done, it can be calculated according to equation (5), where 2.5 × 10-20cm 2/mol:
 | （5） |
since and respectively represent the number density of particles of acetone and isoprene, in units, it can be further converted to volume fractions of acetone and isoprene, the calculation formula is (6):
breath acetone/isoprene volume fraction = | （6） |
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (7)
1. A double-expiration molecule measuring method based on cavity ring-down spectroscopy comprises the steps of measuring the main components, the content and the absorption cross section of human respiratory gas, and is characterized by comprising the following steps:
s1, carrying out respiratory interference analysis on main components in respiratory gas;
s2, screening M (M is more than or equal to 2, and M is a natural number) target elements serving as breathing markers, and selecting laser wavelength for measuring the target elements;
and S3, removing respiratory interference elements.
2. The method of claim 1 for dual-expiratory-molecule measurement based on cavity ring-down spectroscopy, comprising:
s11, respectively measuring the respiratory gas content of the human body at an absorption cross section of 257nm, wherein the respiratory gas content comprises four atmospheric molecules of nitrogen, water, oxygen and carbon dioxide, and the contents are respectively as follows: nitrogen (N2, 78.04%), water (H2O, 6%), oxygen (O2, 16%), carbon dioxide (CO 2, 5%);
s12, measuring the content of the inorganic component with higher content, wherein the content is as follows: ammonia (NH3, 0-2 ppmv), methane (CH4, 2-10ppmv), carbon monoxide (CO, 1-10 ppmv), nitric oxide (NO, 10-50 ppmv), nitrous oxide (N2O,1-20 ppmv), isoprene (C5H8, 50-200 ppmv), acetone (C3H8O, 0-1 ppmv), ethane (C2H6, 0-10 ppmv), pentane (C5H12, 0-10 ppmv),
methanol (CH3OH, 0-10 ppbv), ethanol (C2H5OH, 0-10 ppbv), propanol (C3H7OH, 0-10 ppbv);
s13, excluding the respiratory gas with the absorption section of 0 at 257nm, and analyzing the interference influence of the rest respiratory gas on the target element serving as the respiratory marker.
3. The method of claim 2, wherein the method comprises the following steps:
s21, screening 2 target elements serving as breathing markers: isoprene and acetone;
and S22, according to the data measured in S11, S12 and S13, carrying out respiratory disturbance analysis on oxygen, carbon dioxide and nitrous oxide which disturb target elements in respiratory gas.
4. The method of claim 3, wherein the method comprises the following steps:
s31, eliminating the influence of oxygen and carbon dioxide interfering with target elements in the breathing gas by a background deduction method;
s32, performing direct elimination treatment on nitrous oxide interfering with target elements in the breathing gas;
s33, eliminating the influence of acetone on isoprene through a double-expiration molecule measuring system based on cavity ring-down spectroscopy on the interference between target element isoprene and the interior of acetone.
5. The method of claim 4, wherein the method comprises the following steps: the double-expiratory molecular measurement system based on the cavity ring-down spectrum comprises a 266nm measurement module and a 257nm measurement module, wherein each measurement module is provided with a respective laser output system, a pressure-controlled vacuum cavity, a high-reflection mirror, a data acquisition and analysis module and a sample introduction system; the 266nm measurement module and the 257nm measurement module share one data analysis module, the laser output system is composed of a laser with the emergent wavelength of 266nm or 257nm, the laser emits laser light and enters the vacuum cavity through the first reflector and the second reflector, 99% of the laser light is reflected back and forth between the first high reflector 7 and the second high reflector 8, and a small part of the laser light transmitted from the second high reflector 8 is collected by the photomultiplier after being reflected by the fourth reflector 4 and the third reflector 3 and then enters the data analysis module for data processing.
6. The method of claim 5, wherein the method comprises: s33 includes
S331, measuring the concentration of acetone in the gas sample by using a 266nm laser;
s332, calculating the absorption intensity of the acetone at 257nm, and deducting the absorption intensity of the acetone from the overall absorption intensity at 257nm to obtain the effective absorption intensity of the isoprene at 257 nm.
7. The method of claim 6, wherein the method comprises: s332 includes
First, in the 266nm module, the ring down time for background air in the vacuum chamber 22 was measured
After the measurement is finished, the molecular pump 27 is used for pumping the background air in the vacuum cavity 22 away, and high-purity nitrogen is used for flushing the vacuum cavity 22 for three times;
then, collecting respiratory gas of a subject, and slowly and uniformly blowing the lung gas into the vacuum cavity by the subject through a disposable mouthpiece;
the gas sample is introduced into the vacuum chamber 22 to an atmospheric pressure, and the ring-down time at this time is measured
Calculating the particle number density of breath acetone according to the formula (1)
Wherein
The length of the cavity is 50cm,
at the speed of light 3 x 108m/s，
The absorption cross section of acetone at 266nm is 4.5 x 10-20 cm2/mol，
Subsequently, in a 257nm module, the ring down time for background air in the vacuum chamber 23 was measured
After the measurement is finished, the molecular pump 26 is used for pumping the background air in the vacuum cavity 23 away, and high-purity nitrogen is used for flushing the vacuum cavity 23 for three times;
thereafter collecting the subject's breathing gas;
the testee blows the lung gas into the vacuum cavity slowly and uniformly through the disposable mouthpiece,
the gas sample is introduced into the vacuum chamber 23 to an atmospheric pressure, and the ring-down time at this time is measured
Calculating the effective absorption of acetone and isoprene at 257nm according to the formula (2)
According to S31, formula (2) uses the background subtraction method to subtract the influence of oxygen and carbon dioxide, so that the effective absorption at 257nm
Is caused by respiratory acetone, respiratory isoprene and respiratory nitrous oxide together, and neglects the weak absorption of nitrous oxide at 257nm, namely:
in the formula (4), the first and second groups,
having been obtained by the first measurement step, it can be calculated according to equation (4)
Wherein
Is 3.412 x 10-20 cm2/mol：
In the formula (3), it is known
And
thus, can calculate
，
To obtain
Then, according to the formula (5), the calculation can be performed
Wherein
Is 2.5 x 10-20 cm2/mol：
Due to the fact that
And
respectively represent the number density of particles of acetone and isoprene in
It can be further converted to volume fractions of acetone and isoprene, calculated as (6):
。
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